एक धात्विक छड़ की तापमान T1 °C पर प्रारंभिक लंबाई L1 है, जो तापमान T2 °C पर बढ़कर L2 हो जाती है। रेखीय प्रसार गुणांक (α) के लिए निम्नलिखित में से कौन सा सूत्र सही है?

Small gaps are deliberately left between consecutive steel rails on a railway track to:

Given below are two statements, one labeled as Assertion (A) and the other as Reason (R). Select the correct answer from the options below. Assertion (A): A very hot glass cracks when cold water is poured onto it. Reason (R): Glass expands when heated and contracts when cooled.